The long-term goal of this research is to elucidate the neural mechanisms underlying some cognitive processes in motor behavior. The combined behavioral-neurophysiological experiment is used. Monkeys are trained to perform certain behavioral acts, and then the electrical activity of single cortical neurons is recorded simultaneously with their performance. This experiment provides for a direct study of the relations between neuronal populations and behavior. Specific objectives are focused on the role of frontal and parietal cortical areas in the control of spatial characteristics of movement. These areas are explored in the behaving monkey, and the activity of their neurons studied under conditions of varying complexity in the motor and cognitive aspects of behavior. For the motor part, animals make movements aimed at targets or follow moving targets. For the cognitive part, the predictability of pursuit tracking is manipulated, the selection of certain targets among others is varied (by varying the probabilities of reward associated with each possible target), the rules of translation of stimulus configuration into a motor act are modified (e.g., to make a movement at 90 degrees to a given stimulus), and sequences of movements are generated from memory. A versatile 3-D or 2-D tracking apparatus provides for adequate degrees of freedom for the arm movements in space. A PDP11/04 computer allows control of the animal's behavior and the collection of neural and other data (trajectory of the arm, activity of muscles, eye movements, etc.). A PDP11/34 computer of this research is to understand the representation of task-related cell properties in the cortical areas under study. For that purpose, micro-electrode tracks into the cortex are marked and identified, and the location of cells with particular properties estimated. It is hoped that a detailed analysis of the location of neurons with specific functional properties in the different cortical layers and the cortical surface will lead to a partial understanding of the nature of their cortical representation.